1. Field of the Invention
This invention relates to an optical scanning device suitable for application to an information recording apparatus which utilizes, for example, an electrophotographic photosensitive medium to record the output of a computer or which reproduces pre-stored image information.
2. Description of the Prior Art
A rotational polygon mirror has chiefly been used as the above-described optical scanning device. However, the rotational polygon mirror has suffered from the disadvantage that it requires a correcting means for the falling of the mirror surface or that deviations are created in the optical path system by mechanical vibration. Also, to enhance the resolving power of the printed image by an information recording apparatus using the rotational polygon mirror or to increase the output speed of such apparatus, it has been necessary to increase the number of revolutions of the polygon mirror to several tens of thousandths of r.p.m. and it has not been easy to rotate the polygon mirror stably. In addition, the necessity of enhancing the accuracy of the polygon mirror has unavoidably led to a bulky size and accordingly heavy weight of the device, and the required high accuracy of shape of the polygon mirror itself and the required high accuracy of the driver therefor have resulted in a high cost of the device.
On the other hand, devices using an acoustic optical deflector or an electric optical deflector instead of a rotational polygon mirror to make the devices compact are known. An example of such a device is disclosed in U.S. Pat. No. 3,514,534. However, these optical scanning devices have a small deflection angle in spite of having a feature that they are capable of high-speed deflection, and therefore, commercially available information recording apparatus using such optical scanning devices are not yet known.
The assignee hereof developed a novel beam spot point scanning device by utilizing the thin film waveguide path light integrating technique and proposed it in U.S. application Ser. No. 228,744 filed Jan. 27, 1981 now U.S. Pat. No. 4,425,023 issued Jan. 10, 1984. This beam spot point scanning device is an epoch-making one which is compact and capable of high-speed scanning, but the scanning angle thereof is not sufficient for the device to be used in an information recording apparatus.
There is also an information recording apparatus using an optical fiber tube (OFT), but this is disadvantageous as a high-speed, high-quality information recording apparatus in respect to resolving power and intensity of light.